As is known in the art, AlGaN/GAN high electron mobility transistors (HEMTs) are increasingly being used for applications requiring high-frequency, and high-power. In order to realize the potential of these HEMT devices, it is necessary to achieve low-resistance, good edge acuity and reliable ohmic contacts. Most low resistance ohmic contacts used in devices use Au as the top layer to reduce sheet resistance and decrease oxidation during the high temperature anneal needed to achieve the lowest specific contact resistivity.
The presence of Au in a silicon manufacturing facility can be a serious contamination concern that can cause catastrophic yield problems. For applications requiring processing of GaN device wafers in environments that require Au-free processes such as in CMOS silicon fabs, Au contamination is a serious concern.